FRUIT AND KITCHEN GARDENS NEAR PARIS. 



225 



Fine sand 



Roots and vegetable remains 

 Humus 



Carbonate of lime . 

 Matter soluble in cold water 



62- 

 20' 

 16- 



0- 8 



1- 2 



100-0 



The above can only be called good sandy peat with a mere 

 trace of lime in the form of carbonate. The water employed is 

 spring water. These substances apparently constitute the only 

 source whence the plants derive their luxuriance ; but in this 

 respect they so far exceed others in similar soil, that it is evi- 

 dent they must have an additional large supply of nourishment 

 to that afforded by peat soil and water nearly pure. 



The large stone-built' vault below the beds happened to be 

 empty when we were at Meudon, and we had an opportunity of 

 satisfactorily examining it. The boarding over-head was, of 

 course, somewhat decayed, from the action of the gases arising 

 from the dung, and in various places the old roots of the pine- 

 plants were hanging where they had insinuated themselves be- 

 tween the boards. When this vault is filled, or nearly so, wirh 

 fermenting dung, an immense quantity of ammoniacal and car- 

 bonic acid gases must be constantly generated ; and they must 

 as constantly find means of escaping, not readily by the stone 

 walls, but very easily by the boarding under the soil. Ammo- 

 niacal gas passes through the pores of wood much quicker than 

 common air or other gases do. Liebig states, ' Organic Che- 

 mistry,' p. 85, that ammonia, " When in a volatile state, is in a 

 great measure lost before it can be imbibed. When fixed, in 

 the state of salts, its volatility is overcome, and not the smallest 

 portion of the ammonia is lost to the plants, for it is all dis- 

 solved by water and imbibed by the roots." From the quantity 

 of carbonic acid gas evolved with ammonia during the con- 

 tinued fermentation of the materials, carbonate of ammonia must 

 be abundantly formed. This smelling salt every person knows 

 is very volatile ; but it will be in great measure absorbed by the 

 moisture of the soil as it ascends into the latter. It has been 

 proved that water is capable of absorbing 780 times its bulk of 

 ammoniacal gas. 



It was stated that the water employed was spring water, 

 nearly pure. Unless distilled, no water is perhaps absolutely 

 pure, since it always dissolves more or less of the substances 

 with which it comes in contact. The water near Paris owes its 

 hardness to the presence of gypsum. This circumstance maybe 

 of some importance as regards the Pine-growing at Meudon. 

 " Gypsum (sulphate of lime) and other sulphates convert the 

 carbonate of ammonia into the more fixed sulphate, which re- 



VOL. II. Q 



